.alpha.-Amylases (.alpha.-1,4-glucan-4-glucanohydrolases, EC 3.2.1.1) constitute a group of enzymes which catalyze hydrolysis of starch and other linear and branched 1,4-glucosidic oligo- and polysaccharides.
There is a very extensive body of patent and scientific literature relating to this industrially very important class of enzymes. A number of .alpha.-amylase such as Termamyl-like .alpha.-amylases variants are known from, e.g., WO 90/11352, WO 95/10603, WO 95/26397, WO 96/23873 and WO 96/23874.
Among more recent disclosures relating to .alpha.-amylases, WO 96/23874 provides three-dimensional, X-ray crystal structural data for a Termamyl-like .alpha.-amylase which consists of the 300 N-terminal amino acid residues of the B. amyloliquefaciens .alpha.-amylase and amino acids 301-483 of the C-terminal end of the B. licheniformis .alpha.-amylase comprising the amino acid sequence (the latter being available commercially under the tradename Termamyl.TM.), and which is thus closely related to the industrially important Bacillus .alpha.-amylases (which in the present context are embraced within the meaning of the term "Termamyl-like .alpha.-amylases", and which include, inter alia, the B. licheniformis, B. amyloliquefaciens and B. stearothermophilus .alpha.-amylases). WO 96/23874 further describes methodology for designing, on the basis of an analysis of the structure of a parent Termamyl-like .alpha.-amylase, variants of the parent Termamyl-like .alpha.-amylase which exhibit altered properties relative to the parent.